<!DOCTYPE html>
<div>The blue square should be at the top-left corner of the iframe.</div>
<iframe srcdoc="
  <!DOCTYPE html>
  <body style='writing-mode: vertical-rl; overflow: scroll; margin: 0'>
    <div style='position: absolute; top: 0; left: 0; width: 100px; height: 100px; background: blue'></div>
  </body>">
</iframe>
